The invention relates to a fire safety assembly for use in air ventilation, circulation, heating or conditioning systems.

It is known to use air ventilation, circulation, heating and conditioning systems to transport air throughout buildings and vehicles.

According to a first aspect of the invention, there is provided a fire safety assembly comprising an air flow guide structure for air ventilation, circulation, heating or conditioning, wherein the air flow guide structure includes an internal air cavity configured to permit air to flow therethrough, and the fire safety assembly further comprising a fire protection apparatus, wherein the fire protection apparatus includes:

a barrier device arranged to permit air to flow through the internal air cavity, the barrier device configured to be selectively activatable to form a sealing barrier so as to adapt a part or whole of the internal air cavity into a sealed cavity, and

a fire retardant supply device including a source of fire retardant, the fire retardant supply device including a supply device actuator configured to be actuatable to activate a supply of the fire retardant from the source of fire retardant into the sealed cavity.

For the purposes of this specification, a fire retardant is defined as a substance capable of delaying or stopping the spread of a fire. Preferably the fire retardant is a gaseous fire retardant, such as carbon dioxide.

Preferably the sealing barrier is configured to be made of fire-resistant material.

The air flow guide structure may be or may include any air passageway for air ventilation, circulation, heating or conditioning. The air flow guide structure may be or may include, but is not limited to, an air ventilation structure (e.g. an air ventilation cavity), an air conduit, an air shaft, an air duct, an air tunnel, or an air pipe. Typically, an air flow guide structure interconnects different sites so as to allow the flow of air between the different sites.

In the event of a fire occurrence, there is a risk of the fire spreading from one site to one or more other sites via the internal air cavity of the air flow guide structure. Furthermore, the narrow space of the internal air cavity contributes to a faster air flow velocity and therefore a faster progression of the fire through the internal air cavity of the air flow guide structure, with a readily available supply of atmospheric oxygen maintaining the chemical reaction of combustion.

The formation of the sealing barrier so as to adapt a part or whole of the internal air cavity into the sealed cavity acts to physically inhibit the spread of the fire via the internal air cavity of the air flow guide structure. However, several issues can arise, which are: i) the fire may breach the sealing barrier due to a loss of fire resistance of the sealing barrier; ii) the barrier device only forms a partial sealing barrier which thereby provides one or more gaps for the fire to move past the sealing barrier, or iii) gaps in the sealing barrier are formed by physical changes to, or differential movement of, the air flow guide structure as a result of the fire. By employing the fire retardant supply device to supply the fire retardant into the sealed cavity, any fire that has entered the sealed cavity can be readily prevented from spreading further through the internal air cavity of the air flow guide structure.

The combination of the barrier device and the fire retardant supply device in the fire protection apparatus therefore enhances the overall fire resistance of the fire safety assembly of the invention, which may result in a gain of crucial extra time to react appropriately to the fire occurrence.

In addition, the fire safety assembly of the invention may be manufactured offsite by assembling a new fire protection apparatus and a new air flow guide structure, or may be constructed onsite by retrofitting a new fire protection apparatus to an existing air flow guide structure.

In embodiments of the invention, the fire retardant supply device may include a containment vessel configured to store the source of the fire retardant. In such embodiments, the containment vessel may be arranged to be located inside the internal air cavity. This not only results in a more compact and lightweight fire safety assembly, but also enables the quick supply of the fire retardant from the containment vessel into the sealed cavity, thus improving the effectiveness of the fire protection apparatus. In addition, the containment vessel is easy to install, repair, replace, and decommission.

In further such embodiments, the containment vessel may be configured to store the fire retardant at above room pressure. Storing the fire retardant under pressurised conditions enables automatic release of the fire retardant from the containment vessel into the sealed cavity. The storage pressure of the stored fire retardant can be adjusted to control the rate of release of the fire retardant from the containment vessel. In other embodiments of the invention, the source of the fire retardant may be located outside the internal air cavity. The fire retardant supply device may include: at least one conduit configured to connect the source of fire retardant to the internal air cavity; and at least one conduit valve coupled to the or each conduit to selectively allow and block a transfer of the fire retardant from the source of fire retardant into the internal air cavity.

Locating the source of the fire retardant outside the internal air cavity not only provides greater flexibility in the design of the source of the fire retardant, since the source of the fire retardant is not constrained by the shape and size of the internal air cavity, but also makes it easier to replenish the source of the fire retardant, since there is no need to obtain access to the internal air cavity.

In embodiments of the invention, the fire retardant may be selected so that, when the fire retardant is in gaseous form, it has a density that is higher or lower than the density of oxygen or air. Selecting such a fire retardant allows the gaseous fire retardant to occupy a specific portion of the internal air cavity while displacing oxygen-containing air to the other portion of the internal air cavity, which results in the formation of a gaseous fire retardant barrier that blocks a fire from accessing any available oxygen in the sealed cavity. This thereby provides a mechanism for suppressing the spread of a fire which has entered the sealed cavity. The choice of density of the fire retardant in gaseous form depends on whether a fire is expected to enter the internal air cavity from above or below.

In further embodiments of the invention, the fire retardant may be selected so that the supply of the fire retardant from the source of fire retardant into the sealed cavity reduces oxygen concentration in the sealed cavity to a level which is incapable of supporting combustion. This advantageously provides another mechanism for suppressing the spread of a fire which has entered the sealed cavity.

The configuration of the supply device actuator may vary so long as the supply device is configured to be actuatable to activate a supply of the fire retardant from the source of fire retardant into the sealed cavity. For example, the supply device actuator may be selected from a group including: a mechanical actuator; a valve actuator, a heat-activatable actuator; a bimetallic actuator; an electrical actuator; and a combination of two or more thereof. In still further embodiments of the invention, the air flow guide structure may be partly or wholly made of a material capable of undergoing a chemical reaction to release a fire retardant substance. Such a material is preferably configured to undergo the chemical reaction in response to a product or phenomenon resulting from a fire occurrence, such as heat, a temperature rise, smoke, an infra-red emission. This enables the release of additional fire retardant into the sealed cavity which further increases the overall fire resistance of the fire safety assembly of the invention.

The fire protection apparatus may include at least one fire detector. For the purposes of this specification, a fire detector is defined as a detector capable of detecting a fire occurrence by sensing a product or phenomenon resulting from the fire occurrence, such as heat, a temperature rise, smoke, an infra-red emission.

In a preferred embodiment of the invention, the supply device actuator is configured to be responsive to a detection of a fire occurrence by the or each fire detector so that, in response to the detection of the fire occurrence, the supply device actuator activates the supply of the fire retardant from the source of fire retardant into the sealed cavity. This enables the automatic supply of the fire retardant from the source of fire retardant into the sealed cavity in response to the fire occurrence taking place.

The or each fire detector may be configured to be in wired or wireless communication with the supply device actuator. Such configurations may be used in embodiments of the invention in which the or each fire detector is configured to, upon detecting the fire occurrence, provide fire detection information and/or a control signal to the supply device actuator.

Optionally the fire protection apparatus may include an actuator controller programmed to selectively control actuation of the supply device actuator to activate the supply of the fire retardant from the source of fire retardant into the sealed cavity. The provision of the actuator controller provides proactive and precise control over the actuation of the supply device actuator, which can be used to improve the responsiveness of the fire protection apparatus. The actuator controller may be used in combination with a sensor to monitor the supply device actuator and provide feedback on the state of the supply device actuator.

In another preferred embodiment of the invention, the actuator controller is configured to be responsive to a detection of a fire occurrence by the or each fire detector so that, in response to the detection of the fire occurrence, the actuator controller controls the supply device actuator to activate the supply of the fire retardant from the source of fire retardant into the sealed cavity.

The or each fire detector may be configured to be in wired or wireless communication with the actuator controller, and the actuator controller may be configured to be in wired or wireless communication with the supply device actuator. Such configurations may be used in embodiments of the invention in which the or each fire detector is configured to, upon detecting the fire occurrence, provide fire detection information to the actuator controller, and the activator controller may be configured to provide a control signal to the supply device actuator.

The barrier device may include at least one controllable activator that is configured to selectively activate the barrier device to form the sealing barrier. The provision of the or each controllable activator provides proactive and precise control over the formation of the sealing barrier, which can be used to improve the responsiveness of the fire protection apparatus.

According to a second aspect of the invention, there is provided a fire safety assembly comprising a cladding system, the cladding system including an air flow guide structure for air ventilation, wherein the air flow guide structure includes an internal air cavity configured to permit air to flow therethrough, and the fire safety assembly further comprising a fire protection apparatus, wherein the fire protection apparatus includes a barrier device arranged to permit air to flow through the internal air cavity, the barrier device configured to be selectively activatable to form a sealing barrier so as to adapt a part or whole of the internal air cavity into a sealed cavity, wherein the barrier device includes at least one controllable activator that is configured to selectively activate the barrier device to form the sealing barrier.

The aforementioned advantages of the barrier device and controllable activator(s) of the first aspect of the invention and its embodiments apply mutatis mutandis to the barrier device and controllable activator(s) of the second aspect of the invention and its embodiments.

In a preferred embodiment of the second aspect of the invention, the internal air cavity is provided between at least one cladding member (e.g. at least one cladding panel) and a structural wall of the cladding system. It will be appreciated that it is not essential for the internal air cavity to be directly adjacent the cladding member(s) or structural wall, and it may be the case that one or more other cladding system components, such as insulation panels, may be arranged between the internal air cavity and the cladding member(s) or structural wall.

Each of the following features are applicable to embodiments of the first and second aspects of the invention in which the barrier device includes at least one controllable activator that is configured to selectively activate the barrier device to form the sealing barrier.

As mentioned, the fire protection apparatus may include at least one fire detector. As also mentioned, for the purposes of this specification, a fire detector is defined as a detector capable of detecting a fire occurrence by sensing a product or phenomenon resulting from the fire occurrence, such as heat, a temperature rise, smoke, an infra-red emission.

In a preferred embodiment of the invention, the or each controllable activator is configured to be responsive to a detection of a fire occurrence by the or each fire detector so that, in response to the detection of the fire occurrence, the or each controllable activator activates the barrier device to form the sealing barrier. This enables the automatic formation of the sealing barrier in response to the fire occurrence taking place.

The or each fire detector may be configured to be in wired or wireless communication with the or each controllable activator. Such configurations may be used in embodiments of the invention in which the or each fire detector is configured to, upon detecting the fire occurrence, provide fire detection information and/or a control signal to the or each controllable activator.

The fire protection apparatus may include an activator controller programmed to selectively control the or each controllable activator to activate the barrier device to form the sealing barrier. The activator controller may be used in combination with a sensor to monitor the or each controllable activator and provide feedback on the state of the or each controllable activator.

In another preferred embodiment of the invention, the activator controller is configured to be responsive to a detection of a fire occurrence by the or each fire detector so that, in response to the detection of the fire occurrence, the activator controller controls the or each controllable activator to activate the barrier device to form the sealing barrier. The or each fire detector may be configured to be in wired or wireless communication with the activator controller, and the activator controller may be configured to be in wired or wireless communication with the or each activator. Such configurations may be used in embodiments of the invention in which the or each fire detector is configured to, upon detecting the fire occurrence, provide fire detection information to the activator controller, and the activator controller may be configured to provide a control signal to the or each controllable activator.

Depending on the requirements of the fire safety assembly, the or each fire detector may be located in the vicinity of the air flow guide structure, or in a remote location away from the air flow guide structure. The former enables the fire protection apparatus to be responsive to a fire occurrence taking place in the vicinity of the air flow guide structure, while the latter enables the fire protection apparatus to be responsive to a fire occurrence taking place in a remote location away from the air flow guide structure.

The configuration of the barrier device to enable formation of the sealing barrier may vary so long as the barrier device is selectively activatable to form a sealing barrier so as to adapt a part or whole of the internal air cavity into a sealed cavity.

In embodiments of the invention, the barrier device may include an expandable barrier material that is activatable by an external stimulus so as to expand to form the sealing barrier. For example, the expandable barrier material may be a heat-activatable barrier material that is activatable by the external stimulus in the form of heat so as to expand to form the sealing barrier. Such an expandable barrier material is commonly referred to as an intumescent material.

Preferably the expandable barrier material is configured to be activatable by an external stimulus associated with a product or phenomenon resulting from a fire occurrence, such as heat, a temperature rise, smoke, an infra-red emission. This enables the passive and autonomous activation of the barrier device to form the sealing barrier without requiring any active control, thus reducing the complexity of the fire protection apparatus.

Alternatively, in embodiments of the invention employing the use of the expandable barrier material, the barrier device may include a first controllable activator configured to selectively provide the external stimulus to the expandable barrier material to form the sealing barrier, the first controllable activator including a source of the external stimulus. This enables the active control of the barrier device to form the sealing barrier using the expandable barrier material.

In further embodiments of the invention, the barrier device may include a mechanical barrier that is mechanically activatable to form the sealing barrier. The provision of the mechanical barrier results in a resettable barrier device which permits the fire safety assembly to be restored to its original state to allow air to again flow through the internal air cavity of the air flow guide structure. In contrast, the expandable barrier material is usually removed and replaced in order to restore the fire safety assembly to its original state.

In such embodiments of the invention employing the use of the mechanical barrier, the barrier device may include a second controllable activator configured to selectively activate the mechanical barrier to form the sealing barrier, the second controllable activator including a mechanical actuator. This enables the active control of the barrier device to form the sealing barrier using the mechanical barrier.

The fire safety assembly of the invention may be used in a wide range of applications and equipment requiring the use of an air flow guide structure for air ventilation, circulation, heating or conditioning, wherein the air flow guide structure includes an internal air cavity configured to permit air to flow therethrough. For example, the fire safety assembly of the invention may be used in an occupant structure, a non-occupant structure, a building structure, a non-building structure, or a vehicular structure.

It will be appreciated that, in embodiments of the invention employing the use of multiple controllers, the multiple controllers may be independent of each other, or may form part of the same control system. Such a control system may additionally include a central or global controller configured to communicate with each of the multiple controllers.

It will be also appreciated that at least one embodiment of a given aspect of the invention may also be used in combination with at least one embodiment of the other aspect of the invention.

It will be further appreciated that the use of the terms“first” and“second”, and the like, in this patent specification is merely intended to help distinguish between similar features (e.g. the first and second controllable activators), and is not intended to indicate the relative importance of one feature over another feature, unless otherwise specified. Preferred embodiments of the invention will now be described, by way of non-limiting examples, with reference to the accompanying drawings in which:

Figure 1 shows a cladding system for a building;

Figure 2 shows a fire safety assembly according to a first embodiment of the invention;

Figure 3 shows a barrier device and a fire retardant supply device of a fire protection apparatus of the fire safety assembly of Figure 2;

Figure 4 shows a fire that is located under the fire safety assembly of Figure 2;

Figure 5 shows a containment vessel of the fire safety assembly of Figure 2;

Figure 6 shows a phase diagram of carbon dioxide;

Figure 7 shows a carbon dioxide barrier that is blocking a fire from reaching oxygen-containing air in a sealed cavity of the fire safety assembly of Figure 2;

Figure 8 shows a variation of sealed cavity pressure with oxygen concentration for a sealed cavity of the fire safety assembly of Figure 2;

Figure 9 illustrates ISO fire temperature-time curves for standard, external and hydrocarbon fires;

Figure 10 shows a fire safety assembly according to a second embodiment of the invention; and

Figure 11 shows a fire safety assembly according to a third embodiment of the invention.

The figures are not necessarily to scale, and certain features and certain views of the figures may be shown exaggerated in scale or in schematic form in the interests of clarity and conciseness.

The following embodiments of the invention describe the use of exemplary fire safety assemblies comprising a cladding system that includes an air ventilation structure for air ventilation, but it will be appreciated that the working principle of each of the following embodiments of the invention is applicable mutatis mutandis to other applications and equipment requiring the use of an air flow guide structure for air ventilation, circulation, heating or conditioning.

Figure 1 shows a cladding system for a building. The cladding system includes an external cladding panel 12 attached to the exterior of a structural wall 14 of the building. The external cladding panel 12 and structural wall 14 are arranged to define an air ventilation structure with an internal air cavity 16 provided between the external cladding panel 12 and the structural wall 14. The height of the air ventilation structure may span several storeys of the building.

The cladding system performs a number of functions for the building, such as air ventilation, thermal performance, and acoustic insulation. In particular, for the ventilated cladding system, the provision of the air cavity 16 between the cladding panel 12 and the structural wall 14 reduces moisture content and removes thermal bridges. Steady ventilation of the air cavity 16 can be achieved by the displacement of air flow, which allows for the removal of a high percentage of moisture. This displacement of air flow is created by the progressive heating of the air in the air cavity 16, which rises due to a difference in densities.

As shown in Figure 1 , in the event of a fire 18 reaching the cladding system, there is a risk of the fire 18 entering the air cavity 16 which can then provide a path for the fire 18 to quickly spread up to higher storeys of the building. This exposes the higher storeys to the risk of fire, especially if windows in the higher storeys are compromised. The narrow space of the air cavity 16, which may typically vary between 15 mm and 125 mm in width, contributes to a faster air flow velocity and therefore a faster progression of the fire 18 through the internal air cavity 16, with a readily available supply of atmospheric oxygen maintaining the chemical reaction of combustion. Confinement of a flame within the air cavity 16 can result in the elongation of the flame as it seeks oxygen and fuel to support the combustion process.

A fire safety assembly according to a first embodiment of the invention is shown in Figure 2 and is designated generally by the reference numeral 20. The fire safety assembly 20 of Figure 2 comprises the cladding system shown in Figure 1 , and further comprises a fire protection apparatus. The fire protection apparatus is designed to slow down or stop the spread of fire via the internal air cavity 16 of the air ventilation structure of the cladding system.

The fire protection apparatus includes a barrier device 22 and a fire retardant supply device 24.

The barrier device 22 includes strips of intumescent material placed (e.g. by painting or coating) around the back face of the cladding panel 12, as shown in Figure 3. The width of each strip may be, for example, 50 mm. The intumescent material is heat-activatable so that it expands upon exposure to heat. The intumescent material is arranged so that, when it is in its unexpanded form, it does not fill the gap between the cladding panel 12 and the structural wall 14, thus permitting air to flow through the internal air cavity 16. After being exposed to heat from a nearby fire 18, the intumescent material expands to fill the gap between the cladding panel 12 and the structural wall 14, so that the expanded intumescent material forms a barrier which encloses and seals off part of the internal air cavity 16. In this manner the intumescent material functions as a barrier material that is activatable to form a sealing barrier so as to adapt a part of the internal air cavity 16 into a sealed cavity. It is envisaged that, in other embodiments of the invention, the intumescent material may be replaced by another type of expandable barrier that is activatable by an external stimulus so as to expand to form the sealing barrier. The external stimulus may be associated with a product or phenomenon resulting from a fire occurrence, such as heat, a temperature rise, smoke, an infra-red emission.

Aside from the formation of the sealing barrier, non-flammable gases such as carbon dioxide and ammonia are released upon expansion of the intumescent material, which adds to the fire resistance of the fire safety assembly 20. Commercially available intumescent materials activate and swell at temperatures in the range of 110°C to 120°C, which are reached within the first moments of a fire after ignition. Thus, the intumescent material can be relied upon to form the sealed cavity very soon after a fire approaches.

Typical intumescent materials have an expansion ratio of 50: 1 , which means that a 1 mm thick strip of intumescent material will expand to a thickness of 50 mm upon being activated by heat. As stated above, typical widths of an air cavity of an air ventilation structure in a cladding system may vary between 15 mm and 125 mm. For such air cavity widths, the required thickness of the intumescent material to adequately form the sealed cavity may range between 0.3 and 2.5 mm. The associated fire resistance times may be between 30 to 90 minutes depending on the thickness of the intumescent material, with fire resistance times of 120 minutes achievable in some instances.

The formation of the sealing barrier so as to adapt a part of the internal air cavity 16 into the sealed cavity acts to physically inhibit the spread of the fire 18 via the internal air cavity 16 of the air ventilation structure, as shown in Figure 4. However, several issues can arise, which are: i) the fire 18 may breach the sealing barrier due to a loss of fire resistance of the sealing barrier; ii) the barrier device 22 only forms a partial sealing barrier which thereby provides one or more gaps for the fire 18 to move past the sealing barrier, or iii) gaps in the sealing barrier are formed by physical changes to, or differential movement of, the air ventilation structure as a result of the fire 18.

The fire retardant supply device 24 includes a containment vessel attached (e.g. by using brackets and fasteners) to the back face of the cladding panel 12, as shown in Figure 3, so as to be located inside the internal air cavity 16. More specifically, the containment vessel is positioned on the cladding panel 12 so as to be located inside the sealed cavity when it is formed. It is envisaged that, in other embodiments of the invention, the containment vessel may be arranged in a different way to be located inside the internal air cavity 16, such as being attached to the structural wall 14 instead of the cladding panel 12.

A fire retardant in the form of liquid carbon dioxide 26 is stored in the containment vessel under pressurised conditions at room temperature. The fire retardant supply device 24 further includes a supply device actuator in the form of a thermally actuated valve which regulates release of carbon dioxide from the containment vessel.

It is envisaged that, in other embodiments of the invention, the carbon dioxide may be replaced by another type of fire retardant.

In the embodiment shown in Figure 5, the thermally actuated valve includes a wound bimetallic coil 28 which is designed to expand and contract based on the bimetallic effect. Expansion of the coil 28 causes the thermally actuated valve to open to permit the carbon dioxide to exit the containment vessel. Contraction of the coil 28 causes the thermally actuated valve to close to block the carbon dioxide from exiting the containment vessel. The coil 28 may be made of a stainless steel-aluminium bilayer. The coefficients of thermal expansion of 304 and 316 stainless steels range between 16 pm/m/K and 17 pm/m/K, while the coefficient of thermal expansion of aluminium ranges between 21 pm/m/K and 24 pm/m/K. In other embodiments of the invention, it is envisaged that the wound bimetallic coil 28 may be replaced by a bimetallic strip that bends upwards with increasing temperature to open the valve and bends downwards with decreasing temperature to close the valve.

At room temperature, the thermally actuated valve is closed to seal the containment vessel and thereby prevent release of the carbon dioxide from the containment vessel. When the thermally actuated valve is exposed to heat from a nearby fire, the increase in temperature of the thermally actuated valve results in the expansion of the coil 28 which in turn causes the thermally actuated valve to open, thus permitting the carbon dioxide to exit the containment vessel. Since the containment vessel is located inside the sealed cavity, the carbon dioxide is released from the containment vessel into the sealed cavity.

Referring to the phase diagram of carbon dioxide shown in Figure 6, it can be seen that, for carbon dioxide to exist as a liquid at room temperature (which is typically 20°C), the stored carbon dioxide in the containment vessel must be pressurised to at least 58 atm, which is approximately 5.9 N/mm ² . Upon opening of the thermally actuated valve, the pressure differential forces the liquid carbon dioxide 26 into the sealed cavity whereupon it depressurises and expands as a gas.

Carbon dioxide at atmospheric pressure is almost 1.5 times as dense as air. As a result, as shown in Figure 7, the carbon dioxide 30 released into the sealed cavity occupies the lower portion of the sealed cavity while displacing the oxygen-containing air 32 towards the upper portion of the sealed cavity. This is beneficial because, if the sealing barrier is breached by a fire 18 approaching from under the sealed cavity, the carbon dioxide 30 acts as a barrier that blocks the fire 18 from accessing the displaced oxygen-containing air 32 in the upper portion of the sealed cavity. Accordingly, the spread of the fire 18 through the internal air cavity 16 may be inhibited without having to completely fill the sealed cavity with carbon dioxide.

It may be that the carbon dioxide barrier is unable to persevere throughout the duration of a fire since the increasing temperature, and hence enthalpy, of the multi-gaseous system encourages considerable molecular transport, and therefore mixing, between the released carbon dioxide and the incumbent air. However, even if the carbon dioxide barrier diminishes with increasing temperature and mixing of the gases, the introduction of carbon dioxide into the sealed cavity provides another mechanism by which the spread of fire can be impeded. Provided that sufficient carbon dioxide is released into the sealed cavity, the mixing of the released carbon dioxide and the incumbent air can reduce the oxygen concentration in the sealed cavity to a level that can no longer support combustion and thereby cannot sustain the fire. Reducing the oxygen concentration in air from the naturally-occurring 21 % (by volume) to 15% will extinguish most fires.

In order to reduce the oxygen concentration in the sealed cavity, the total volume of the incumbent air and the released carbon dioxide is required to be increased by releasing carbon dioxide from the containment vessel into the sealed cavity. Releasing the carbon dioxide into the sealed cavity, which has a fixed volume, results in an increase in pressure inside the sealed cavity. As shown in Figure 8, assuming the air inside the sealed cavity is initially at 1 atm, achieving an oxygen concentration of 15% via the release of carbon dioxide into the sealed cavity will increase the pressure within the sealed cavity to 1.4 atm, which is negligible. Even reducing the oxygen concentration to 10% via the release of carbon dioxide into the sealed cavity will only raise the pressure to 2.1 atm, or 0.21 MPa, which is well within the limits of structural performance of typical cladding panel materials.

The working principle of the fire safety assembly 20 of Figure 2 is therefore based on the initial formation of the sealing barrier so as to adapt part, or whole, of the internal air cavity 16 into the sealed cavity, which is followed by the introduction of a fire retardant into the sealed cavity in order to inhibit the spread of fire through the internal air cavity 16. This working principle is applicable mutatis mutandis to inhibit the spread of fire through the internal air cavity of other types of air flow guide structures for air ventilation, circulation, heating or conditioning. Such air flow guide structures may be configured for use in an occupant structure, a non-occupant structure, a building structure, a non-building structure, or a vehicular structure.

Preferably, in order to allow for the possibility of some of the stored liquid carbon dioxide 26 remaining in the containment vessel, the containment vessel should store more than the amount of liquid carbon dioxide required for reducing the oxygen concentration to a level that can no longer support combustion.

Figure 9 illustrates ISO fire temperature-time curves for standard, external and hydrocarbon fires. It can be seen from Figure 8 that a standard or external fire can lead to temperatures in the range of 600°C to 800°C within 10 to 20 minutes of ignition, and that a hydrocarbon fire can lead to temperatures in the region of 1 100°C within 10 to 20 minutes of ignition.

Since the internal pressure inside the containment vessel will increase with temperature, the containment vessel should be designed to be capable of withstanding the increase in pressure resulting from the temperature rise caused by the fire occurrence. This is important to not only ensure the steady release of the carbon dioxide into the sealed cavity, but also to prevent uncontrolled bursting or explosion of the containment vessel which could compromise the integrity of the cladding panel 12 and intumescent material. The design of the containment vessel may involve selecting the dimensions, shape and/or material of the containment vessel. An exemplary material for the containment vessel is stainless steel, such as 304 and 316 stainless steels, which provides the containment vessel with the required strength to withstand the internal pressure at elevated fire temperatures.

The cladding panel 12 may be formed of a range of materials, such as non-combustible materials and materials of limited combustibility (e.g. mineral-fibre-based products and glass wool), thermoset materials (e.g. polyurethane foam, phenolic foam, polyisocyanurate foam), thermoplastic materials (e.g. expanded polystyrene, extruded polystyrene), natural fibres (e.g. wood fibre, cork, sheep wool, cellulose), and recycled materials (e.g. recycled paper, shredded rubber, recycled glass).

Alternatively, the cladding panel 12 may be partly or wholly made of a material capable of undergoing a chemical reaction to release a fire retardant substance. Such a material may consist of, or include, calcium carbonate.

At temperatures around 850°C, calcination begins to occur whereby the calcium carbonate decomposes into calcium oxide and carbon dioxide. Referring to the fire temperature-time curves of Figure 9, it is expected that a cladding panel 12 made of calcium carbonate would undergo calcination during a fire occurrence to release the carbon dioxide. This enables the release of additional fire retardant into the sealed cavity which further increases the overall fire resistance of the fire safety assembly 20.

Optionally the thermally actuated valve may be replaced by an electrically actuated valve which mechanically opens or closes upon receipt of an electrical control signal. The fire protection apparatus may include an actuator controller programmed to selectively control actuation of the electrically actuated valve. The actuator controller may be used in combination with a sensor to monitor the electrically actuated valve and provide feedback on the state of the electrically actuated valve.

It is envisaged that, in other embodiments of the invention, the barrier device 22 may include a controllable activator configured to selectively provide the external stimulus to the barrier material to form the sealing barrier. With reference to the intumescent material, the controllable activator may include a sparking mechanism for producing sparks, which provides the heat required to activate the intumescent material.

It is envisaged that, in still other embodiments of the invention, the intumescent material may be replaced by a mechanical shutter that is mechanically activatable to form the sealing barrier. The provision of the mechanical shutter results in a resettable barrier device 22 which permits the fire safety assembly 20 to be restored to its original state to allow air to again flow through the internal air cavity 16 of the air ventilation structure. In such embodiments of the invention, the barrier device 22 may include a controllable activator configured to selectively activate the mechanical barrier to form the sealing barrier, wherein the controllable activator includes a mechanical actuator.

Further optionally the fire protection apparatus may include an activator controller programmed to selectively control the controllable activator to activate the barrier device 22 to form the sealing barrier. The activator controller may be used in combination with a sensor to monitor the controllable activator and provide feedback on the state of the controllable activator.

It will be appreciated that each numerical value given for the embodiment of Figure 2 is merely chosen to help illustrate the working principle of the invention, and may be replaced by another numerical value.

A fire safety assembly according to a second embodiment of the invention is shown in Figure 10 and is designated generally by the reference numeral 120. The fire safety assembly 120 of Figure 10 is similar in structure and operation to the fire safety assembly 20 of Figure 2.

The fire safety assembly 120 of Figure 10 differs from the fire safety assembly 20 of Figure 2 in that, in the fire safety assembly 120 of Figure 10, the containment vessel is located outside the internal air cavity 16. In order to supply the carbon dioxide 26 from the containment vessel into the sealed cavity, the fire retardant supply device 24 includes a pipe 34 interconnecting the containment vessel and the internal air cavity 16, wherein the pipe 34 is positioned so as to be connected to the sealed cavity when it is formed. A pipe valve 36 is provided in the pipe 34 in order to control a flow of the carbon dioxide 26 from the containment vessel into the sealed cavity.

A fire safety assembly according to a third embodiment of the invention is shown in Figure 11 and is designated generally by the reference numeral 220. The fire safety assembly 220 of Figure 11 is similar in structure and operation to the fire safety assembly 20 of Figure 2.

The fire safety assembly 220 of Figure 11 differs from the fire safety assembly 20 of Figure 2 as follows. In the fire retardant supply device 24, the thermally actuated valve is replaced by an electrically actuated valve which mechanically opens or closes upon receipt of an electrical control signal 38.

The barrier device 22 includes a controllable activator configured to selectively provide the external stimulus to the barrier material to form the sealing barrier. More specifically, with reference to the intumescent material, the controllable activator includes an electrically controlled sparking mechanism for producing sparks, which provides the heat required to activate the intumescent material. It is envisaged that, in other embodiments of the invention, the intumescent material and the sparking mechanism may be respectively replaced by a mechanical shutter and an electrically controlled mechanical actuator.

The fire protection apparatus includes a control system 40. The control system 40 includes: an actuator controller programmed to selectively control actuation of the electrically actuated valve; and an activator controller programmed to selectively control the controllable activator. In the embodiment shown, the control system 40 is configured to communicate wirelessly with the electrically controlled sparking mechanism and the electrically actuated valve, so that the control system 40 can send control signals 38 to the electrically actuated valve and the electrically controlled sparking mechanism. The control system is equipped with a wireless transmitter for transmitting wireless communications. The electrically controlled sparking mechanism and the electrically actuated valve are each equipped with a wireless receiver for receiving wireless communications.

The fire protection apparatus includes a plurality of fire detectors 42, such as temperature sensors and light obscuration smoke sensors, at key locations around the building to detect a fire occurrence. As stated above, a fire detector 42 is defined as a detector capable of detecting a fire occurrence by sensing a product or phenomenon resulting from the fire occurrence, such as heat, a temperature rise, smoke, an infra-red emission. The fire detectors 42 are each equipped with a wireless transmitter for transmitting wireless communications. The control system 40 is equipped with a wireless receiver for receiving wireless communications.

In the event of a fire 18 being detected in the building, at least one fire detector 42 communicates wirelessly with the control system 40 so as to provide fire detection information 44 to the control system 40. In turn the control system 40 sends control signals 38 to the electrically controlled sparking mechanism and the electrically actuated valve in order to initiate the formation of the sealing barrier so as to adapt part or whole of the internal air cavity 16 into the sealed cavity and then enable the release of carbon dioxide from the containment vessel into the sealed cavity. In this manner the sealed cavity is formed and the carbon dioxide is released into the sealed cavity in advance of the fire approaching the internal air cavity 16.

It is envisaged that, in other embodiments of the invention, the fire retardant supply device 24 may be omitted from the fire safety assembly of Figure 11. It is also envisaged that, in still other embodiments of the invention, the fire retardant supply device 24 of the fire safety assembly of Figure 11 may be replaced by the fire retardant supply device 24 of the second embodiment shown in Figure 10.